Democrat John Kerry's (search) campaign ad says, "Under George Bush, 3 million Americans have lost their jobs." When gains over the last few months are factored in, the number is around 1.8 million.

President Bush's commercial claims, "John Kerry will raise taxes by at least $900 billion in his first 100 days in office." The candidate has never proposed such an increase, and the figure is based on GOP calculations.

Welcome to the world of political advertising, where half-truths, exaggerations and distortions can make it difficult for voters to tell fact from fiction.

"There's more misleading stuff popping up than you can swing at," said Brooks Jackson, a former reporter and the director of the Annenberg Political Fact Check (search), a Web site that evaluates the accuracy of campaign rhetoric. "Voters, be aware: These guys have a constitutional right to lie to you as much as they want."

Advisers for Bush and Kerry defend their candidate's ads as accurate interpretations of the other's record or views, and each campaign typically releases pages of documents backing up its claims. Yet, independent fact-checkers have found flaws on both sides, and the campaigns often accuse each other of fiction.

While federal regulations require truth-telling when advertisers sell soap on television, they don't regulate what candidates for federal office say about each other. As a result, they can bend or twist the truth by selectively choosing facts that suit their agendas, giving voters only a slice of the picture.

Much of the murkiness is caused by the realities of political advertising. Strategists often have only 30 seconds to project their candidate's message. That means the context, details and explanation surrounding an accusation or an appeal end up on the cutting room floor, leaving only vague sound bites. Most of the time, that's by design.

"Ads in politics are by definition about advocating the best possible representation of your position and the worst possible representation of your opponent's position," said Carter Eskew, a Democrat who helped create ads for Al Gore in 2000.

But voters are smart enough to know that they are only getting one side of the story in an ad, argued Eskew, who says they "bring a pretty sophisticated and cynical filter to it."

Still, it's more difficult for voters to figure out the truth when ads contain "lies of omission," said Christian Grose, a campaign media expert at Lawrence University in Appleton, Wis.

Bush's campaign has based its ads, which portray Kerry as weak on national security and favoring tax increases, on isolated votes and quotes plucked from the Democrat's 19-year Senate career.

Charlie Black, a veteran GOP strategist and former chairman of the Republican National Committee (search), said some facts — like an opponent's voting history — can't be disputed. "A record's a record," he said.

However, some of Bush's ads are based on Senate votes that Kerry made in the context of larger bills. Other ads cite votes Kerry cast decades ago or past comments that may not reflect his current positions.

Bush's latest ad claims "Kerry has repeatedly opposed weapons vital to winning the war on terror: the Bradley Fighting Vehicles, Patriot missiles, B-2 Stealth bombers, F-18 Fighter Jets and more." Those accusations are drawn, in part, from Kerry votes in the 1980s and 1990s against a few monstrous Pentagon spending bills, which included money for various weapons systems.

Another ad accused Kerry of wanting to raise gas taxes by 50 cents a gallon — a claim based on a fleeting 1994 quote by Kerry published in two Boston newspapers.

Yet, the truth isn't clear-cut in some of Kerry's ads either.

One recent commercial criticizing Bush on his abortion stance claimed the Supreme Court is "one vote away from outlawing a woman's right to choose." That was true at one point, but of the current justices, a 6-3 majority has indicated that women have a constitutional right to end their pregnancies.

Another ad claimed that Bush said outsourcing jobs "makes sense." He never uttered that phrase. It was included in an annual report from his economic advisers, the preface of which Bush signed. A look at the full quote indicates there was a limited circumstance in which Bush's advisers said importing goods and services "makes sense."

Positive ads can be misleading, too, when candidates puff up their resumes. But those are fairly rare this year.

Grose's advice to voters: "If you want to learn about a candidate, a 30-second ad is not the best place to go!"