WASHINGTON - On any given day, Republicans call Hillary Rodham Clinton a deeply flawed future presidential candidate.

Or a formidable one.

Or, with the right amount of Republican-led scrutiny, one who might not run after all.

As the former secretary of state, first lady and New York senator prepares for a high-profile book tour in June, Republicans are using a variety of approaches to try to define Clinton and drive down the mostly positive approval ratings she built while in President Barack Obama's Cabinet.

At the same time, the Republican Party is building an anti-Clinton infrastructure that aims to undercut her appeal more than two years ahead of the presidential election.

"Ultimately our goal is to stop Hillary Clinton,'' said Garrett Marquis of the Stop Hillary PAC, which formed last year and has raised $500,000 and says it has 250,000 enlisted supporters.

"If we can do that by dissuading her from running for president in the first place, then we'll consider our effort a success,'' Marquis said. But if Clinton runs, Marquis said, the extra time will help ``build a campaign to stop her.''

Clinton's record at the State Department is likely to receive a public dissection when she begins promoting "Hard Choices,'' her memoir of her time as the nation's top diplomat.

In speeches, she has described it as a series of tough calls. The book is expected to discuss the raid that killed Osama bin Laden, the Obama administration's diplomacy with China, Iran and the Middle East, and the September 2012 attack that killed four Americans at a diplomatic compound in Benghazi, Libya.

Republicans say Clinton's tenure at the State Department lacked any notable accomplishment and that many of the choices were bad ones.

When Clinton recently criticized Nigeria's Boko Haram for its mass kidnappings of young girls, Republicans said she had failed to label the group a foreign terrorist organization while she was in charge.

On Benghazi, Clinton's testimony to a Senate committee - and her famous sound bite, "What difference does it make?'' - remains a formidable issue among Republican activists and the basis for countless fundraising pitches. House Republicans are launching a select committee that will further probe the Benghazi attack.

Researching Clinton's past has been a major task for America Rising LLC, a Republican group founded by Matt Rhoades, Mitt Romney's former campaign manager.

The group has raised money through a website called StopHillary2016.org and has 20 paid trackers who follow Democratic candidates in search of "gotcha'' moments that can shift momentum in campaigns. Executive director Tim Miller said the group will send camera-carrying trackers to some of Clinton's book events.

"My feeling is that Hillary Clinton is already running for president,'' Miller said.

America Rising, he said, has sought to ``provide a counterbalance and hold her accountable so that she doesn't just get a platform to kick off a presidential campaign without the scrutiny that should rightly come along with that.''

Stop Hillary PAC, meanwhile, warns on its website that by 2016, "it will be too late to stop Hillary. We've got to hold her accountable right now.''

Marquis said the group, led by a Colorado state senator, Ted Harvey, aims to mobilize voters against a future Clinton campaign and hopes to have 1 million supporters by the end of 2014.

And then there's the notion that Clinton might not run.

"Given the month she just had, I actually doubt very much whether she actually will run for president,'' Republican National Committee Chairman Reince Priebus said last Sunday on NBC television's ``Meet the Press.''

He didn't add that the past month was rocky largely because a prominent Republican operative questioned Clinton's mental and physical health and House Republicans renewed their inquiry into Benghazi.

Many Democrats say Republicans attack Clinton almost nonstop because they see her as the strongest possible presidential opponent by far, and that it conveniently fires up conservative voters who are crucial in the fall elections. Polls show Clinton leading all the leading 2016 Republican presidential contenders.

"Republicans are singularly focused on turning out their base,'' said Mo Elleithee, a spokesman for the Democratic National Committee. He said harping on Benghazi, the Internal Revenue Service, the president's health care law ``or something to do with the Clintons'' is one tactic.

Steve Schmidt, a veteran strategist on Republican presidential campaigns, said Republicans may be erring by focusing on the Clintons now. The criticisms are unlikely to dissuade her from running, he said, and the ruckus could backfire on Republicans in states such as Kentucky, where Obama is unpopular but the Clintons are widely liked. Former President Bill Clinton has campaigned alongside Alison Lundergan Grimes, the Democrat trying to oust Senate Republican leader Mitch McConnell.

"The degree to which Hillary Clinton is positioned in front and center, and not the president, I think it hurts Republicans at the end of the day,'' Schmidt said.