WASHINGTON (AP) — Sen. Marco Rubio is renewing his outreach to tea party supporters and his advocacy for GOP causes as he struggles to repair his image as a conservative standard-bearer.

The shift comes after the potential 2016 presidential candidate pushed the Senate to approve an immigration overhaul bill that's been panned by some on the right who could be crucial to his future.

Rubio joined about 50 conservative activists and other lawmakers Tuesday at a meeting of the Senate's tea party caucus, putting him in a room with representatives of grassroots activists who helped fuel his unlikely Senate victory in 2010.

The Florida senator, considered a formidable presidential candidate in 2016 if he seeks the White House, spent months advocating for a comprehensive immigration reform proposal but has been largely absent from lobbying efforts since the process moved to the House. Instead, he has returned to conservative causes he has supported in the past, highlighting his opposition to President Barack Obama's health care law by pushing for an elimination of its funding, backing a measure to place more restrictions on U.S. funding of the United Nations and opposing the White House's choice to lead the Labor Department.

It comes as some of his supporters cite frustration with his backing of the Senate immigration plan.

"His immigration bill is much more of a letdown than him taking a sip of water in the response to the State of the Union," said Kellyanne Conway, a Republican pollster, referring to the senator's reach for a water bottle during his February speech.

Participants said Rubio was warmly received at the closed-door meeting and discussed immigration reform and Obama's health care law. The meeting was also attended by Republicans such as Texas Sen. Ted Cruz, Minnesota Rep. Michele Bachmann and Wisconsin Sen. Ron Johnson. Sen. John McCain, R-Arizona, also stopped by the meeting to advocate for immigration reform and told activists he was a "Ronald Reagan Republican — and that's a big tent party. There should be plenty of room for everybody."

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Johnson said that Rubio "understood and I think Republicans and conservatives understand our immigration system is broken and it needs to be fixed so he showed some real political courage. I think he'll probably be rewarded in the end for that courage."

Eighteen months before voters begin considering the Republican field, it remains difficult to predict whether Rubio's stance on immigration could be a liability with voters. Two potential Senate rivals, Cruz and Rand Paul of Kentucky, voted against the immigration reform bill and have been critical of the measure as they begin appearing in early voting states like Iowa and South Carolina. In Iowa on Friday, Cruz said the Senate bill continued "the same mistakes of the past," citing a 1986 reform law that is anathema to conservatives now.

The tea party meeting was bringing together several lawmakers and representatives of a variety of tea party organizations and other conservative groups, including the anti-tax Americans for Tax Reform and 60 Plus Association, which advocates on issues relevant to the elderly. While tea party activists said they were frustrated with Rubio's advocacy for the Senate bill, which has been rejected by House Speaker John Boehner, R-Ohio, many said they still view the senator as a stalwart on benchmark issues like federal spending and opposition to the health care law.

"It's not like he's speaking to a foreign audience. He's speaking to his family," said Niger Innis, a chief strategist for the TeaParty.net, which is helping plan the meeting.

For months Rubio was by far the most prominent salesman for the Senate's immigration bill in the conservative community, appearing multiple times weekly on conservative talk radio shows, Fox News Channel and other programs to promote the bill.

He met with House Republicans and fellow GOP senators to try to win them over, and convened meetings of leading Republicans from think tanks and outside groups to try to build consensus around the need for reform.

Rubio didn't win over everyone, but his involvement was seen as partly responsible for the much friendlier initial response from conservatives to the legislation compared to Congress' last attempt to write a comprehensive immigration bill, which failed in 2007.

Throughout, Rubio was largely flying solo. The other Republican authors of the bill — McCain and Jeff Flake of Arizona and Lindsey Graham of South Carolina — couldn't match Rubio's conservative bona fides or his popularity with the tea party, and largely left the conservative outreach to him. That put Rubio far out on a limb with the bill, which passed the Senate on a strong bipartisan vote of 68 to 32 last month.

Almost immediately, the legislation was rejected by House conservatives, leaving its future unclear and Rubio's efforts potentially frustrated. The bill's unpopularity with the right seemed to grow, raising the question of whether Rubio's advocacy would help him politically by creating a reservoir of goodwill with Latino voters — or turn out to have been a spectacular miscalculation.

"He should have distanced himself from that bill earlier on. I'm not sure why he even voted for it," said Everett Wilkinson, a Florida-based chairman of the National Liberty Federation, a tea party organization. Despite unhappiness with Rubio on immigration, Wilkinson said his stances on other issues important to conservatives are "spot on."

In the weeks since the bill cleared the Senate, Rubio's silence on the bill has been impossible not to notice. He's stopped issuing statements on the legislation and promoting it in interviews, and when the Senate authors of the bill summoned business lobbyists to a meeting last week to push them to step up their campaign in the House, Rubio was conspicuous by his absence.

Some — including House Republicans — have interpreted Rubio's silence as more than that.

"As people have learned about the Senate bill its favorability has gone down," said Rep. John Fleming, R-La. "Sen. Rubio, who was the tip of the spear on that, has shut up about it completely, he doesn't even talk about it anymore. It's unpopular."

Rubio's aides insist the senator is not trying to distance himself from the immigration issue, but simply giving the House space to do its work.

"I think anybody that questions Sen. Rubio's commitment to immigration reform has been living in a cave for the last seven months," said Rubio spokesman Alex Conant. He said the House should be given "the time and space to consider its own immigration legislation and he won't be part of any effort to pressure the House."

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Associated Press writer Catherine Lucey in Des Moines, Iowa, contributed to this report.