Is this a mutiny or just a shot across the bow? Republicans on Capitol Hill might not be in full revolt against President Bush, but the signs are not good for what’s left of his second-term agenda.

Last week’s GOP-led Senate vote to nudge Bush toward an Iraq withdrawal plan could be just the beginning of the end for his long run of party loyalty in Congress.

There are many opportunities ahead for additional tests of the administration’s strength among Republican lawmakers. On banning torture, cutting spending, drilling for Alaskan oil and extending tax cuts, the president’s party faces a growing divide between what he wants and what the voters might want in next year’s midterm battle for control of Congress.

Most alarming for Republicans is the slippage among their own party’s voters, especially moderates and women. Polls show these voters troubled by the president’s stubbornness on Iraq and his rightward turn on the environment, social spending and abortion rights.

In a CNN/USA Today/Gallup Poll released Nov. 17, a majority of those questioned said they were less likely to back a congressional candidate supported by Bush. Only 9 percent — including just 21 percent of Republicans — said they would be most likely to support a GOP candidate who agrees with Bush “on almost every major issue.”

It could not have been worse timing for the White House when 41 Republicans joined 37 Democrats in a Senate vote last week to require quarterly administration reports and set detailed pre-conditions for pulling troops out of Iraq — and declaring that the year until Election Day should be “a period of significant transition” to Iraqi sovereignty. This slap at Bush came just as he was trying to dig out of his crash in the polls by saying it is only Democrats who disagree with his handling of Iraq. But with most Republicans signing on to this unprecedented (in the Bush era) assertion of congressional war oversight, his stepped-up attacks on Democrats fell flat.

Senate Republicans found a new twist to the adage about partisanship stopping at the water’s edge. Here, it was party loyalty stopping at the water’s edge.

Bush has little time to heed his party’s message before the next round of tests challenging his power over Congress. The budget-savings package emerging on the Hill is proving to be a vehicle for GOP moderates to assert themselves. Already, the spending cuts are getting watered down in an effort to hold Republican votes.

Even the president’s pet project, extending his 2003 tax cuts, is not sailing as smoothly as expected. Again, his troubles start with lawmakers in his own party. Senate leaders desperately tried to salvage the overall package by stripping an extension of the break on capital gains and dividends, and scaling back tax benefits for big oil companies.

Another Bush priority — opening the Arctic National Wildlife Refuge to oil drilling — also has moderate Republicans nervous. They ran it aground in the House and vowed to fight it to the end.

There’s nothing complicated about this. Fear of voter backlash against the Bush agenda in next November’s congressional elections is driving today’s GOP resistance. Party operatives are counseling candidates to gingerly find daylight between themselves and the president so they can stay close to swing voters as well as Republican moderates, who make up more than a third of the party’s base.

These voters prefer conservative-leaning stability from their elected leaders, but they balk when the GOP veers too far to the right. Swing-state lawmakers, such as Sen. Rick Santorum of Pennsylvania, are especially at risk. It was telling that he managed not to be on stage during Bush’s recent visit to his state.

While there is plenty in the president’s domestic agenda to complicate Republican campaigns, it is the war on terrorism — once a battering ram against Democrats — that is becoming the unshakable albatross.

A few Republican senators even tripped up a deal to extend the anti-terrorism Patriot Act, once a point of pride for GOP lawmakers in their campaigns against Democrats who opposed it. And the administration’s determination to exempt the CIA from a ban against torture is giving party loyalists fits, as they gauge public reaction, particularly among women alarmed by this proposal.

Of course, Hill Republicans would prefer to face voters next year with a popular president at their side, and most are loath to vote against his wishes and further undermine his public standing. But at the end of the day, they will fret most about their own careers.

If GOP lawmakers continue challenging Bush to distance themselves from him, it will be out of fear that they have no choice, and it would be an unmistakable sign that, at least among his own political troops, they have little hope he can regain his swagger.

Contributing Editor Craig Crawford is a news analyst for MSNBC, CNBC and “The Early Show” on CBS. He can be reached at ccrawford@cq.com.