 -- This week we asked David Axelrod -- the former senior adviser to President Obama who now works as a CNN senior political commentator -- five questions via email before his appearance on the "This Week" roundtable.

Q: You have not been hesitant to critique Hillary Clinton on Twitter. And it's something that has not gone unnoticed, which I am sure you know. Callum Borchers of the Washington Post wrote, referring to you recently, "it sure looks like he’ll continue to be a thorn in her side and a go-to source for her opponents opposition research teams." So, why have you chosen to publicly criticize her? Do you worry about inflicting damage?

AXELROD: My role at CNN is as a commentator not a surrogate. I run a non-partisan Institute of Politics at the University of Chicago. I've tried to offer observations based on my experience as someone who has covered presidential elections as a journalist and helped run them as a strategist. So, for example, when the pundit class was writing that Hillary Clinton was in jeopardy in the summer, I said I would buy a ton of her stock because I thought her assets as a candidate were being greatly undervalued. I praised her performances in the first debate and before the Benghazi committee. But if I see things I feel are off, I'll note those, as well. I've been similarly candid about every campaign, Republican and Democrat. I know, like and deeply respect Hillary. I worked for her in her Senate race. But my job today is not to act as a factotum for hers or any campaign. It's to call them as I see them. I'm humble enough to know that neither my praise not my critiques will impact on the outcome of her campaign.

Q: Are you disappointed that Vice President Joe Biden did not make a bid for the presidency? How would his entrance have changed the race?

AXELROD: I love Joe Biden. I had a chance to work with him during the campaigns and my two years in the White House. In my opinion, he's been a great Vice President -- impeccably loyal, a candid adviser and a guy who has handled some of the administration's most difficult assignments. Having said all that, I know how painful the loss of his son, Beau, was to him and his family. And he knows how demanding a race for president would have been, particularly starting late. I think he made the right decision. Had he run, he would have made it a closer race, three ways. But I'm not sure that the outcome would have been different.

Q: Mitt Romney -- who you spoke with on your podcast -- has said he's not running for president, but he has not stayed out of the public eye. Could you envision a scenario where he jumps into the race?

AXELROD: This Republican race is one for the books--and I'm sure there will be many. The strong anti-establishment movement within the GOP is real, and the center-right, governing conservatives in the race have thus far found little take-up. But more than half the GOP delegates will be selected after March 15, and all of those contests will be winner-take-all. This includes delegate-rich states like California and New York. If there is a winnowing down of the field, a candidate will emerge. If the field does not, a brokered convention is possible, though unlikely. I'm sure if the party approached Romney, he would run. He took some fitful steps toward another candidacy earlier this year. But this scenario seems remote.

Q: Let’s talk about Donald Trump. What explains his success in the polls and do you think he could defeat Hillary if they faced off in the general election?

AXELROD: Donald Trump is the perfect anti-Obama, running in a party that has deep antipathy to the president. He is bombastic, impulsive and unrestrained. His kick-ass, call-names style has found an audience, particularly with non-college educated white men, who have responded with enthusiasm to Trump's nativist, anti-immigrant, anti-trade jeremiads. In an era when so much seems out of our control, he is the proverbial strongman, assuring everyone he'll take care of everything that ails us. We have seen such characters in history before. That said, Trump has high negatives among voters overall, and has commanded about 20 to 30 percent of the GOP vote. Current polling matchup notwithstanding, I believe he would be defeated handily in a general election matchup with Hillary, in part because his anti-immigrant rants have left him with negatives among Hispanic Americans approaching 80 percent.

Q: Is President Obama's strategy to defeat ISIS working?

AXELROD: That is a question better posed to military experts. I am not one. But one thing we should have learned from recent history is to ask the question, "Then what?" We could send in American troops and overrun ISIS. But then what? With Syria in disarray, and the hated [President Bashar] Assad still in power, how long would Americans have to stay and at what cost? By making ourselves the point of the spear, and inserting American ground troops in large numbers, superseding coalition partners from the region, would we be putting ISIS down or fueling a broader jihad? For all the bellicose rhetoric and criticism, I have seen no really distinctive wise and workable alternatives beyond intensifying the strategy already in place.