Speaking in Washington, D.C. on Oct. 20, Former Virginia senator Jim Webb announced he would no longer seek the Democratic party's nomination for president in 2016. (AP)

Former Virginia senator Jim Webb announced Tuesday afternoon that he would no longer pursue the Democratic presidential nomination, saying that he will instead gauge support in the coming weeks for a possible White House bid as an independent candidate.

"More people in this country call themselves political independents than Republicans or Democrats. I happen to agree with them," Webb told reporters at a news conference at the National Press Club in Washington.

"I am withdrawing from any consideration of being the Democratic Party's nominee for the presidency," he said. “This does not reduce in any way my concerns for the challenges facing the country … or my intentions to remain fully engaged in the debates that are facing us."

During a question-and-answer session with reporters following Tuesday's announcement, Webb said he has yet to decide if he will remain a registered Democrat. Acknowledging the tall odds facing an independent presidential bid, he said he and his team would explore whether there is an opening for him to launch such a candidacy. He said he would spend “the next couple weeks talking with people I have not felt comfortable talking with as a Democratic Party candidate.... I feel much freer now, having cleared the air to do that."

The move further narrows a Democratic primary field that has been dominated by former secretary of state Hillary Rodham Clinton and Sen. Bernie Sanders (I-Vt.).

Webb, who served as the secretary of the Navy under President Ronald Reagan, entered the race in July with a heavy focus on foreign policy, highlighting his opposition to the Iraq War while criticizing the Obama administration's military intervention in Libya and its nuclear negotiations with Iran. He was immediately seen as a long-shot candidate but was believed to bring to the race a formidable foreign policy voice to challenge Clinton, whose tenure at the State Department has remained at the heart of her White House bid.

[Monday: Jim Webb may be contemplating running as an independent instead of as a Democrat.]

But the former one-term senator struggled to raise interest in his candidacy over his three-month campaign, polling at 1 percent in the most recent Washington Post-ABC News survey and maintaining a scant campaign schedule, with few campaign events in early-voting states. His announcement follows an underwhelming performance at the first Democratic debate last week, where he was challenged for being out of step with the Democratic base on affirmative action and gun control.

His performance was panned by critics, who said he appeared unprepared for a tough line of questioning; the liberal magazine Mother Jones said he had "misse[d] his moment." A Saturday Night Live skit that aired days after the debate lampooned Webb's frequent complaints to moderator Anderson Cooper that he was not being given as much time to speak as other candidates .

Webb's departure from the field removes its only Vietnam veteran, a fact not lost on Sen. John McCain (R-Ariz.), who has known Webb since before he ran for Senate.

"I've always respected Jim Webb on national security and defense," said McCain. "He obviously has the credentials for the job, including secretary of the Navy. I've been a great admirer of Jim Webb's, for a lot of reasons, including the Vietnam War."

[Graphic:Who's winning 2016?]

According to McCain, Webb's failure to get traction in the Democratic Party said something about who voted in primaries. "I don't know if he ever had a base," the Arizona senator said. "Elizabeth Warren -- she has a base. Sanders has a base. I'm not sure Jim Webb really had that, unless it was with defense-oriented people, and they're more in the Republican Party."

Webb said Tuesday that he had felt marginalized by the Democratic establishment, but that he was “not trying to stand here and attack the Democratic Party."

"There were strong differences of feeling between the hierarchy and myself," he said. "The Democratic Party is heavily invested in the notion of interest-group politics — and interest-group politics can also exclude people who also need a voice in the hallways of power.”

The former senator added that would not attend any future Democratic primary debates and that he is now fully removed from the party's nominating process regardless of whether he formally launches an independent bid. He added that he could foresee an independent candidate beating both Clinton and Republican front-runner Donald Trump.

Shortly after Webb spoke, the Democratic National Committee bade him bon voyage. "Since declaring his candidacy, we've praised Senator Webb's long and distinguished record of service to his country, both in our military and in public office," DNC Chair Debbie Wasserman Schultz said in a statement. "We were glad to welcome him onto the debate stage last week in Nevada and wish him well going forward.”

[July: In uphill 2016 bid, Jim Webb brings conservative bent to Democratic field.]

During the last presidential campaign, Gary Johnson, a two-term Republican governor of New Mexico, had an even rougher experience in his party's primaries. In 2011, he was locked out of all but two televised debates, a marginalization that contributed to his lack of traction. Shortly before the New Hampshire primary, he bolted the GOP for the Libertarian Party and became the highest vote-getter in its history without making much of an impact on the 2012 race overall. That experience gave him some insight for Webb, if the former senator indeed decides to mount a new bid.

"I didn’t go off and run as an independent," Johnson told The Washington Post. "I ran as a Libertarian where you have organization in place in every single state. I think he’s in for a rude awakening -- perhaps he's already taken this into account, but it may be an $8 million endeavor to get on all the ballots. In half the states, it’s easy to do; in the other half you need to put some real money behind it."

Johnson, who has joined other third-party veterans in a lawsuit aimed at expanding the presidential debates beyond the two major-party candidates, said an independent campaign by Webb would struggle to get traction.

"I sure get his frustration with having served and not getting any airtime whatsoever," said Johnson. "Now, the parties are going to ignore him. They’re going to say he doesn’t make any difference whatsoever. That’s what happened with me."

A Federal Election Commission financial disclosure filed last week showed that the Webb campaign had failed to raise the money necessary to run competitively for the nomination. By comparison, Clinton and Sanders have already raised tens of millions of dollars.

For his part, Webb raised nearly $700,000 and spent nearly $400,000, according to the filing. He ended the quarter with just $318,000 cash on hand.