The pressure is on for Vice President Biden to run in 2016. Washington Post chief correspondent Dan Balz explains what Biden needs to do if he decides to compete in the Democratic presidential primary. (Sarah Parnass/The Washington Post)

Democrats loyal to Vice President Biden have a three-word response to the politicians and pundits who say Hillary Rodham Clinton’s performance in Tuesday’s Democratic debate makes a Biden campaign less likely: Not so fast.

Appearing eager to tamp down talk that the window of opportunity for the vice president to launch a campaign nearly closed after the debate, loyalists are taking steps to assure potential supporters that there is still a path to the nomination, however competitive and challenging, if Biden decides to run.

The clearest evidence came Friday as the International Association of Fire Fighters informed the vice president the union will endorse him if he enters the race, according to a source familiar with the union’s thinking. That followed a letter e-mailed late Thursday to Biden’s political support network by former senator Ted Kaufman of Delaware, who said a Biden campaign would be “optimistic,” “from the heart” and unscripted.

“If he runs, he will run because of his burning conviction that we need to fundamentally change the balance in our economy and the political structure to restore the ability of the middle class to get ahead,” Kaufman wrote.

President Obama deflects election questions on Vice President Biden and former Secretary of State Hillary Clinton during a White House news conference. (Reuters)

Even as initial polls showed a bump for Clinton after her performance, Biden’s lingering shadow continued to leave a sense of instability over the Democratic race, leading to questions on the subject for President Obama during a Friday news conference with the South Korean president. “I am not going to comment on what Joe is doing or not doing,” Obama said. “I think you can direct those questions to my very able vice president.”

And in a television interview Friday, Clinton declined to embrace a suggestion from John Podesta, her senior campaign adviser, that Biden must make a decision soon because the race is already engaged. “That’s up to Vice President Biden,” she said on CNN’s “The Lead with Jake Tapper.” “Certainly I’m not in any way suggesting or recommending that the vice president accept any timetable other than the one that is clicking inside of him. He has to make this decision.”

Kaufman’s words were arguably less significant than the author behind them. The former senator — appointed to the seat after his ex-boss became vice president — is Biden’s longest-serving adviser, bridging the divide between the generation of staffers who worked for Biden as a senator in the 1980s and a new crop of lieutenants who came up through the past decade of the family’s public service.

More important, Kaufman has been frequently portrayed as the most reluctant of the trio of inner-circle aides to the vice president to launch a bid and is known to be angry at the frequent portrayals of Biden as being on the brink of announcing his candidacy. A note from him to the alumni network is treated as having more credibility than any leak to the national press corps.

The main issue, still apparently unresolved, remains whether Biden and his family feel ready for the rigors of a presidential campaign so soon after the death of his oldest son, Beau, in May. Nothing Biden has said publicly in recent weeks has suggested an affirmative answer, but he has not addressed the issue directly since before Pope Francis’s visit to the United States last month.

According to those tracking the vice president’s deliberations, a decision could come at any time, although the only certain timetable is the one set by the deadlines for qualifying for primary and caucus ballots throughout the country. Those deadlines began to take effect at the end of the month.

Hillary Clinton, Bernie Sanders and the other candidates took on gun control, Benghazi and other big issues at the first Democratic presidential debate of the 2016 race. Here are the highlights. (Sarah Parnass/The Washington Post)

Outside Biden’s tight circle of advisers, many Democrats have long assumed that, beyond personal and family considerations, the biggest factor in the vice president’s decision-making involved Clinton’s political vulnerability.

A month ago, as controversy over her use of a private e-mail account while serving as secretary of state damaged her image, she appeared seriously weakened. That prompted calls from nervous Democrats, or those in the party never particularly partial to Clinton, for Biden to jump in.

But assessments of Clinton brightened considerably after she delivered an impressive performance in Tuesday’s debate with Sen. Bernie Sanders (I-Vt.), former Maryland governor Martin O’Malley and two other candidates.

Biden loyalists have tried not to be swept up by shifting assumptions about the strength or weakness of the Democratic front-runner, believing she was never as damaged as some were suggesting a month ago.

At the same time, they are not persuaded that this week’s debate fundamentally changed the race in her favor. There is outside evidence backing up that view, including strong interest in Sanders on social media and the fact that the senator from Vermont raised more than $2 million in the 24 hours after the debate.

In recent days, Biden has kept in touch with leaders of key constituency groups, including calls Friday morning. One recipient of a Biden call, who requested anonymity to speak freely about the private conversation, said the vice president actively discussed the emerging campaign strategy, its structure and what constituencies he would win over. Biden believes he has a persuasive message for Democratic voters and would have the resources to run a competitive and potentially lengthy campaign, the call recipient said. Moreover, Biden’s view of the debate, this source said, was that it confirmed that Clinton’s current competition is subpar at best.

Polls and other evidence suggest that if Biden was to enter, the Democratic nomination campaign would quickly become a three-way contest. Clinton would remain the favorite, but it is clear that Sanders has more than enough money to continue well beyond the four earliest states — Iowa, New Hampshire, Nevada and South Carolina.

Biden has told those he has spoken with that he believes he, too, would have the money to remain in the race past those states. It remains unclear what other unions would follow the firefighters in endorsing Biden. “Any conversations I’ve had with the vice president would be private,” Harold A. Schaitberger, general president of the International Association of Fire Fighters, said in a telephone interview Friday night.

None of the first four contests appears ready to tip to Biden, although because he is not a declared candidate, the polls are not reliable. But some of those partial to Biden have seized on a little-remembered fact from 1992 to offer hope that early defeats need not drive a candidate out of the nomination contest.

In that campaign, Bill Clinton lost 10 of the first 11 contests, from early February through the first days of March. He then secured a string of victories in western and Southern caucuses and primaries, followed by wins in Illinois and Michigan that effectively broke the back of his opponents.

Hillary Clinton’s next major event will be an appearance Thursday before the House committee investigating the deaths of four Americans in Benghazi, Libya, in September 2012, along with her e-mail account. That highly charged appearance has taken a turn in her favor as a result of House Majority Leader Kevin McCarthy (R-Calif.) suggesting the goal of the committee had been to weaken her politically.

Then on Oct. 24, Clinton and other Democratic candidates will speak at the Jefferson-Jackson Dinner in Iowa, a quadrennial proving ground for presidential hopefuls. Given the breadth of organizing that Clinton’s team has done in the Hawkeye State, Biden’s advisers assume the event will give her an additional boost, although Sanders will have plenty of supporters there, too.

All that would suggest that Biden could delay announcing a decision until after those two events.

There were many lines in Kaufman’s letter that suggested Biden still wasn’t ready to make a decision, despite the encroaching deadlines.

“I know in the daily ups and down of the political swirl, we all get bombarded with the tactics. So sometimes it’s good to take a step back and get real again. Let’s stay in touch,” Kaufman wrote. “If he decides to run, we will need each and every one of you — yesterday!”