Editor’s Note: David Axelrod, a senior CNN political commentator and host of “The Axe Files,” was senior adviser to President Barack Obama and chief strategist for the 2008 and 2012 Obama presidential campaigns. The opinions expressed in this commentary are his. View more opinion articles on CNN.

CNN  — 

A week ago, Joe Biden seemed to be sailing to the Democratic nomination. His nearly flawless launch had allayed doubts about the durability of his support, his ability to raise enough money and even his desire to enter the fray.

Biden’s shrewd strategic decision to train his fire on Donald Trump from the start, essentially bypassing the primary and jumping to the main event, instantly seemed to solidify his front-runner status. In a party desperate to defeat the President, the former vice president presented himself as the seasoned warrior, suiting up for one last battle to defend the fundamental democratic values and norms Trump has sundered.

The result was an immediate eight-point boost in his lead in national polling, doubling that of his closest competitor, Sen. Bernie Sanders, and lapping the field. The money poured in. Trump signaled his assumption – and, perhaps, concern – that Biden would be his opponent by firing off a fusillade of malign tweets.

Biden’s early strength in primary polls also reflected the value of his partnership with President Barack Obama. It’s an enormous asset with Democrats and, particularly, black voters, who make up a quarter of the primary electorate and could be Biden’s firewall in the nomination battle.

The prevailing question became, “Can Biden be beaten?”

Well, he’s still the front-runner. But after his last, shambling week, the new question is “Can Biden hang on?”

(Both questions are a little foolish at this stage but, hey, it’s what we do!)

The former VP and his campaign sowed new doubts with their clumsily shifting answers on the fundamental issue of federal funding of abortion.

To review, Biden had long supported the Hyde Amendment, a provision in federal law barring the use of federal funds for abortion. He was not alone. Many Democrats have concurred with Hyde, albeit reluctantly, if only to forestall more drastic restrictions.

But recent moves toward draconian limits on abortion in the states, and fears over the future of Roe v. Wade with a new Supreme Court alignment, have created a backlash among abortion-rights voters and Hyde is now a target.

When Biden was asked twice by a woman on the campaign trail whether he would support the repeal of Hyde, he gave her an unqualified yes. But when video of the exchange surfaced last week, his campaign said he had “misheard” the question and still supported the ban.

Twenty-four hours later, after drawing fire from opponents and pleas from supporters, Biden reversed field again and announced his opposition to Hyde.

Compounding the awkwardness of this flip-flop-flip were the post-mortem stories in which Biden’s staff at first appeared to take credit for his change of mind and then said he made the decision himself in the car en route to the dinner at which he announced it.

Politicians flip and flop. That is not news. And every campaign survives occasional bumps in the road that are breathlessly reported yet rarely decisive. Still, this episode revived larger questions about the front-runner, who has twice failed to survive Iowa in previous bids for the presidency.

First, he “misheard the question” may have been an honest answer but probably not the card you want to play too often when your candidate would be 78 the first day he occupies the Oval Office.

So far, Biden has pursued a much lighter schedule than the other candidates. He went an entire 10-day stretch recently without a public appearance, and those he makes are carefully choreographed. He largely has avoided the media or challenging interview settings.

It may be a smart strategy to a point, but the Rose Garden can become a Game of Thorns if the sense grows that the aging candidate is being protected from himself. The campaign is a proving ground to show he is up to the demands of the job.

Second, there is the double-edged sword of longevity.

One of Biden’s assets is that his nearly half-century in politics gives voters a sense of comfort and familiarity.

One of his greatest liabilities is that along with his nearly half-century in politics come countless votes and statements on a wide array of issues. Some have very different connotations in a new era and changing Democratic Party than they did when he made them. Hyde will not be the last.

Taken on its own, the Hyde stumble was hardly fatal. But Biden is ahead, in no small part, because he seems the least risky choice for a party intent on beating Trump. More weeks like the last, and Biden could lose that edge.

The other mixed news for Biden came with the release of the new Iowa Poll, conducted by The Des Moines Register and CNN.

On the upside, Biden is still the Iowa leader, with 24%, eight points higher than Sanders. The bad news is that his support has slipped by a third since December.

Sen. Elizabeth Warren, who has been making steady gains, followed Sanders by a point. Mayor Pete Buttigieg – an asterisk six months ago – stood a point behind Warren at 14%. Sen. Kamala Harris was at 7%, and was the No. 1 “second choice” in the poll, which is more meaningful in a caucus than a primary.

In short, it’s a horse race in Iowa, and Biden, who makes only his second tour there as a candidate on Tuesday, is no lock to win. His supporters report being far less enthusiastic than those of the other top tier contenders, which is important in caucuses where motivation to show up is essential.

For the first months of his campaign, Biden has run as the putative nominee. But with the presumption of leadership comes the expectation of success. Second or third in Iowa would be considered a victory for Warren, Buttigieg or Harris. For Biden, who received just 1% there in 2008, anything less than victory could be the beginning of an unraveling.

Biden bypassed a candidate cattle call in Iowa this weekend and waited to return to Iowa on Tuesday – the same day Trump hits the state. It serves the former vice president’s strategy of turning the page to the general election. And polls continue to show Biden leading Trump in critical states the President needs to win re-election.

But the events of the last week and the Iowa Poll should serve as a warning:

No one is going to hand Biden the Democratic nomination. He’ll have to engage fully and fight for it if he is to get the face-off with Trump he is seeking.