Matt Yeglesias is right - fundamentally Democratic party is contesting 2016 elections on defense. Since Democrats do not have any chance of capturing House in 2016 and chances of getting any razor thin majority in Senate solely dependent on notoriously difficult Democratic constituencies reaching to voting booths; electing Hillary Clinton to the White House is the only political leverage Democrats have in stopping the Republican Agenda. Why would any progressive be scared of Republican Party's agenda with the new crop of Republican presidential contenders who are generally not inclined to undertake George Bush style Iraq hubris? As liberal commentators like Yeglesias and Paul Krugman have been pointing out for a while, the Republican policy agenda is still extra-ordinarily ruinous to this country when one considers what is proposed by GOP contenders. Across the board all of these Republican presidential contenders are proposing Trillions of dollars of deficit inducing tax cuts for rich. Many of these contenders are interested in removing 'full employment' mandate of Federal Reserve Board (referred as Fed), if possible bring back Gold standard and in general dramatically curtail scope and freedom of Fed in tackling an economic crisis. It is as if 'some nice Fed going on USA for you uh, let us whack it and see how it can save common Americans next time'! All these wacky monetary policy prescriptions of Republicans would debilitate Fed and in general would ignite a new global financial crisis.
Breaking up Fed is only one aspect of Republican policy palate. They are not content there and are proposing in general to loosen up whatever relatively weak regulations Frank-Dodd law is imposing on Wall Street; meaning once again American System will be deprived of any regulatory mechanism to avoid next financial crisis and common / poor Americans will face more hardship. Add to that the usual Republican agenda of removing or reducing any safety nets for disadvantaged folks in this country, ending of ObamaCare to throw millions upon millions out of insurance coverage without any alternative and then the picture of proposed Republican calamity is complete.
On this background, saner minds in this country see the need of a non-Republican occupant of the White House. Given the grip of Republican Party on both chambers of Congress, desperation among Democrats in seeing Hillary win is clear.
Naturally, from Republican perspective winning all three leverages of power at Federal level (House, Senate and White House) is like achieving a unique opportunity to 'ram through' the above mentioned Republican agenda. There is no desperation here, but the 'upside' of winning White House on the background of a 'lock' on Congress is obvious and that is what Republican mandarins are aiming for.
So then what are the chances of GOP achieving complete political win in 2016 - i.e. to win White House apart from prevailing in Congress? The answer to that question depends on how does the Trump Candidacy Circus end. If Sen. Ted Cruz wins Iowa and he or any of the other establishment candidates (Sen. Rubio or Gov. Christie or Gov. Kaisch or even Gov. Jeb Bush) drive Republican nomination process to an obvious non-Trump nomination; we know then that it will be a familiar and normal election between a conservative Republican and a Democrat. It is unlikely to be a 'wave election' like 2008 when Americans elected Barack Obama in droves. It will be the 'voter turn out' battle barring exceptional incidence like a terrorist attack or a new economic calamity (both of which will help the Republican candidate).
Things become more uncertain when 'defeat of Donald Trump' is not so emphatic in the Republican nomination process. A narrowly losing Donald Trump has lot more potential to destroy the 'fabric of traditional Republican' party by going 'rogue or extreme'. His rhetoric will become even more explosive to grab that tantalizingly close nomination. He will carve out even more extreme positions pulling all other Republican contenders along with him. Since Republican Party has no ability to withstand the outlandish policy on-slaughter of Donald Trump as there is no political Center in Republican Party left; the moderation of Rubio, Kaisch and others has no chance to sustain the pull of Trump lunacy. Not only will it make difficult for Republicans to win White House in that scenario, it will have negative impact on Congressional races as well handing a surprise advantage to Democrats in that event. This will be the most optimistic scenario for Democrats, especially if by then Hillary has won her nomination in a clean sweep having united Democratic party cohesively behind her.
On the other hand instead of 'barely making to the podium'; if Donald Trump wins the Republican nomination in a clear and emphatic manner, 'inflammatory rhetoric' from Trump will be kind of muted. Republican Party will grumble to unite behind him; but it will have a chance to limit the damage to down ballot races in that event.
Either ways it is clear that the destiny of Republican Party and what happens in American Politics in 2016 is intimately tied to how Trump campaign rolls out in early months of 2016.
 - As a party Democrats have not been doing a competent job in ensuring Democratic control in State level offices and State level chambers. Republican lock at state level continues to drive conservative agenda with impunity. Higher turnout of Democratic voter base is the key for that and Democrats continue to fail in that, exhibit 2014 elections. President Obama put in place an effective infrastructure for voter turn around which delivered him wins both in 2008 and 2012. What is not clear is whether as a party Democrats have inherited this infrastructure or not; suspicion is it has not.
 - It is too bad that Democratic Party Leaders have not been doing a good job in explaining how damaging Republican Policy prescriptions are. President Obama could have used his eloquence on the stump to expose this agenda since for sure common Americans, Democrats & Republicans, are neither in favor of reducing taxes for rich nor interested in destabilizing our existing monetary / financial regulatory framework. If at all, most Americans want to tighten up of regulatory framework on Wall Street and it makes sense given that there is a scant evidence that 'Obama Regulations' constrained any economic growth. Now, sure President Obama would have talked about all this from time to time. But when one considers the 'gold standard in dressing down of Republican agenda - Bill Clinton's speech in 2012 convention'; one understands how much opportunity is lost by Democrats in making a solid case against Republicans in American Elections. For sure, Bernie Sanders is making the argument of economic populism; but his tendency to discount every other issue including national security in lieu of economic inequality does not bring him much wider credibility. Hillary Clinton has shown willingness in espousing sensible economic populism on the campaign trail; but seems like she needs to ratchet up that rhetoric a knob or two. Hillary and Democrats are leaving 'too much on the table' given the utter ineffectiveness as well as potential dangers of Republican economic policy prescriptions.
 - Some are arguing that Donald Trump phenomenon is simply manifestation of tumultuous longer term transformations happening in American Society - loss of privileged position occupied by early White Europeans settlers and their descendants to late and new immigrants of 'color' as well as to other existing minorities like African Americans. This may very well be the case. The question is does such a core level change have to manifest in the fascist fashion of Donald Trump campaign in American Politics? My thinking is there is a lot to do with narcissist personality of Trump for the way our politics is shaping. Besides regardless of this cardinal social change, the fact is economic agenda offered by Republican contenders, including Donald Trump, is equally devastating to these White Americans who are about to become minority. In that sense, the fight against regressive 'rich people' serving agenda of Republicans does not change; it is same for we all Americans. Not for nothing we see so many White Young Americans flocking to Bernie Sanders rally and responding positively to Elizabeth Warren war cries against Wall Street Bankers. The 'great power shift' from White Americans to Colored Minoroties does not free us from fighting 'exclusively rich serving agenda' of the Republican Party. That is a common task for all of us - whites and non-whites alike.