Feb. 7 (Bloomberg) -- John McCain is putting his ``straight talk'' reputation on the line today when he enters a convention full of conservatives who distrust what he has to say.

The Arizona senator will attend the Conservative Political Action Conference, which he snubbed last year, in a bid to unite Republicans after taking a decisive lead in the race for the party's presidential nomination. He has his work cut out.

``The mutual distrust and animosity between McCain and conservative leaders is very deep and very real,'' said David Keene, chairman of CPAC, an annual gathering in Washington of students, activists and policy makers. ``He's not going to solve his problems with one speech. He has to demonstrate over time that he's somebody that be can trusted.''

Keene and other leaders want McCain to declare his opposition to tax increases, his commitment to appoint judges opposed to abortion and gay marriage, and his intention to hire people with loyalty to the movement's principles -- starting with his running mate.

``If he wants to be president, he has to unite the conservative coalition,'' said Tony Perkins, head of the Family Research Council, a Washington-based advocacy group. ``The only way he can do that is by identifying with them and making them believe he understands and believes in their issues and believes in them.''

Fine Line

McCain, 71, said he understands his task. ``I have to talk to them about issues that are important to them,'' he said aboard his ``Straight Talk Express'' campaign bus. While he probably has the Republican nomination assured, he'll need the party's base to be energized to win the general election.

He needs to walk a fine line in courting conservatives, because he risks eroding his support among independents.

``He's going to have to run this two-track campaign,'' said Stu Rothenberg, a Washington analyst. ``It's a balancing act, absolutely.''

McCain's conservative credentials came under fire in recent days from radio talk-show host Rush Limbaugh, while James Dobson, chairman of Colorado Springs, Colorado-based Focus on the Family, a family values-focused group, announced he wouldn't vote for him.

Those attacks underscored the senator's obstacles to winning over this faction -- even though other social and economic conservatives have rallied to his side, including Kansas Senator Sam Brownback and former Texas Senator Phil Gramm.

`United Party'

``We'd like to have a totally united party,'' McCain said. ``But I also realize there are some people who may not be able to support me.''

The enmity between McCain and conservatives has at times become personal. He denounced evangelists Jerry Falwell and Pat Robertson as ``agents of intolerance'' during the 2000 presidential race. He incensed conservatives by sponsoring a campaign-finance law that they say hampered their fund-raising ability, supporting federal funding of stem-cell research and backing a bill to give illegal immigrants a path to citizenship.

McCain rival Mitt Romney is also scheduled to address CPAC today. ``It's going to be a real showdown,'' said Romney spokesman Kevin Madden.

Even before he dominated the Super Tuesday primaries this week and the delegate numbers were added up, McCain was already reconciling with conservatives.

He has vowed to veto any tax increases. That amounts to a ``read my lips'' moment, said Grover Norquist, an advocate of lower taxes, referring to former President George H.W. Bush's 1988 ``no new taxes'' pledge.

Roots

Norquist, who once clashed with McCain over the tax activist's ties to convicted lobbyist Jack Abramoff, said the senator is ``coming back to his Reagan roots,'' after having gone ``AWOL'' by opposing President George W. Bush's tax cuts in 2001 and 2003.

On judicial nominations, McCain faces a tougher sell.

Many conservatives remain upset at his role in a bipartisan ``Gang of 14'' senators that brokered a deal to preserve the right of Democrats to filibuster such nominations -- even though the agreement enabled the confirmations of Bush appointees, including Supreme Court Justice Samuel Alito.

Anger at McCain erupted anew last week amid reports he had privately criticized Alito for wearing his philosophy ``on his sleeve.'' McCain said he doesn't recall saying that.

``The Alito thing is troubling,'' said Keene, chairman of the American Conservative Union. He said conservatives are more interested in hearing McCain say he'd appoint judges who won't ``legislate'' from the bench.

Keene also said McCain must exclude as potential running mates those who conservatives would find objectionable.

Energize Party

``The whole question of securing his base and the Republican disquiet with him makes it almost mandatory that McCain consider going with a conservative running mate who would get those people energized,'' Keene said. ``And given his age, he's likely to be a one-term president anyway.''

Keene said conservatives harbor another concern: ``They fear he doesn't like them and that if he had his druthers, he'd remake the party with them on the outside.''

More than just winning them over, McCain must excite conservatives, said Ralph Reed, the former head of the Christian Coalition who was also implicated in hearings on lobbyist Abramoff that McCain began in 2004.

``I'd sure want to make sure the grassroots of my party are energized,'' Reed said. ``So far they're not.''

To contact the reporter on this story: Edwin Chen in Washington at EChen32@bloomberg.net.

Last Updated: February 7, 2008 00:11 EST