May 16 (Bloomberg) -- President George W. Bush, whose sliding voter-approval ratings threaten to undermine Republicans in this year's elections, is trying to galvanize a political base that's losing enthusiasm for him and his party.

Bush's announcement last night that he plans to deploy thousands of National Guard troops to curb illegal immigration is just one of a series of planned steps intended to rally core supporters.

The White House is also pushing for votes on red-meat Republican economic issues such as more tax cuts, and Bush is threatening to impose his first veto over spending legislation. And the administration is coordinating with Congress on social issues such as a ban on gay marriage and pledging to fill judicial vacancies, looking for confrontations with Democrats.

``Ultimately, we need to remind people that we are still the party of tax cuts, and they are the party that supports partial- birth abortions,'' said Grover Norquist, president of Americans for Tax Reform, a Washington-based group that advocates lower taxes.

While Bush's public-approval ratings have been sinking for more than a year, polls showing increasing dissatisfaction among Republican voters are especially troublesome for party lawmakers facing elections in November. Mid-term congressional elections are often determined by which party does a better job turning out its core voters.

A Gallup organization poll taken May 5-7 found that Bush's approval rating among Republicans fell 11 percentage points to 69 percent from the beginning of the year. A Pew Research Center poll taken last month showed Bush's numbers declining as much among white evangelical Protestants as the general public.

Disappointing Supporters

``Evangelicals have been the very core element of Bush's support and helped him secure the coalitions he needed to win the presidency,'' said Scott Keeter, a Pew polling analyst. ``A president who isn't doing well with his most loyal supporters has a hard time getting lawmakers to pay attention to his agenda.''

Republican activists have voiced frustration over issues including the rise in federal spending and a lack of White House attention to the defense of traditional marriage. And Bush's failed nomination of White House Counsel Harriet Miers to the Supreme Court in 2005 sparked an uproar among conservatives skeptical about her views on abortion, affirmative action and school prayer.

Now, Bush may work with Congress to make good on a pledge from his 2004 re-election campaign and seek a congressional vote to ban gay marriage, the first step toward a proposed constitutional amendment.

Tax Cuts

Also in the cards is a permanent repeal of the federal estate tax and elimination of the 3 percent excise tax on telephones, as well as extending a research tax credit for companies.

The issue of conservative judges is crucial to gaining support even beyond the party's base, said Jay Sekulow, chief counsel for the Washington-based American Center for Law and Justice. He said supporters are pushing the White House to focus attention on filling appellate-court vacancies.

``We had two big victories with the Supreme Court, but the White House can't use that as an excuse to sit back,'' Sekulow said, referring to the appointments of Justices John G. Roberts Jr. and Samuel A. Alito Jr.

Those pleas prompted Bush's top political adviser, Karl Rove, to meet with conservative activists on May 8 at the White House and promise them the president would soon send more judicial nominees to Capitol Hill for confirmation. Three days later, one previously nominated appellate court nominee, White House aide Brett Kavanaugh, was approved by the Senate Judiciary Committee on a party-line vote.

Partisan Warrior

That set the stage for renewed fighting in the Senate over Bush's judicial appointments. Democrats accuse Kavanaugh of being a partisan warrior for Republican causes, including the impeachment of President Bill Clinton.

Tony Perkins, president of the Washington-based Family Research Council, said religious conservatives have been important to Bush for more than just ``values'' issues like abortion and stem-cell research. ``They also form the core of his support on the war on terror, because they implicitly trust that he will do what he has to do to protect them,'' Perkins said.

Bush may have strengthened his hand among supporters with his selection of Michael Hayden, the architect of the National Security Agency's domestic-spying program, as Central Intelligence Agency director.

The government's secret collection of millions of telephone records under that program is backed by 72 percent of Republicans and just 20 percent of Democrats, according to a USA Today/Gallup poll. The survey of 809 adults taken May 12 and 13 showed that 43 percent of Americans overall backed the program. The poll had a margin of error of plus or minus 4 percentage points.

Lashing Back

Concern that a Democratic-controlled Congress may pursue investigations of the White House or seek to impeach Bush has Republican lawmakers lashing back.

Senate Republicans sent a fund-raising letter last week to supporters warning that Democratic majorities would put the fight against terrorism ``on the back burner'' and that ``our worst fears'' could be realized with congressional trials and investigations of Bush.

All members of the U.S. House of Representatives and a third of the Senate are up for re-election, and Republicans are trying to preserve majorities in both chambers.

Democrats would ``call for endless investigations, congressional censure and maybe even impeachment of President Bush,'' Senator Elizabeth Dole of North Carolina wrote.

Anxiety Over Spending

Scott Reed, a Republican consultant who managed former Senator Bob Dole's 1996 presidential campaign, said many Republicans are most upset about federal spending. Spending has soared by 45 percent since Bush took office, the fastest pace since Franklin Roosevelt was president, according to Brian Riedl, a budget analyst at the Heritage Foundation in Washington.

Bush's threat to veto emergency-spending legislation may not be enough to cheer the party, said Pat Toomey, a former Republican congressman who runs the Club for Growth, a Washington group that advocates limited government spending.

Unlike previous threats warning that Bush's advisers would recommend a veto, this one explicitly said the president would reject the legislation being considered by the Senate if spending rises above $94.5 billion for the wars in Iraq and Afghanistan, hurricane relief and pandemic influenza-preparation programs.

``To really rally conservatives,'' Toomey said, ``he's going to have to carry out one of his veto threats.''

To contact the reporter on this story: Holly Rosenkrantz in Washington at hrosenkrantz@bloomberg.net

Last Updated: May 16, 2006 00:07 EDT