Henniker, N.H. ? New Hampshire may be the only state where you can turn on the television and see a commercial in which the Democratic candidate for the Senate lavishes praise on President Bush.

Jeanne Shaheen, the former governor now running for the Senate, expresses her heartfelt support for the war in Iraq and the Bush tax cuts, before repeating the line, “I’ll stand with President Bush.”

The quotes are authentic but horribly out of date. They were uttered in 2002, the first time Shaheen tangled with a young John Sununu for the Senate. Six years after he won that race – barely – Sununu is fighting for his political life in a political climate far less benign for Republicans. His ad, called “Remember,” is designed to raise doubts about Shaheen in the minds of the many independent voters who clearly want to use their Senate vote to send a message of disapproval to Bush.

When they held their first televised debate at New England College here the other night, it was evident that this grudge fight, now six years old and counting, has exhausted the patience and good will of both candidates. They started quarreling with the first question – Sununu supporting the financial rescue package and Shaheen condemning it as a giveaway to Wall Street. And they never stopped. When Sununu tried to detail the changes he’d supported in the bailout to help consumers and investors, Shaheen cut him off. “That’s so much Washington mumbo-jumbo,” she said.

Their fight has drawn heavy outside money from both parties, as Democrats strive for a filibuster-proof 60-vote majority and as Republicans try to save one of their bright future stars. Shaheen, 61, a New Hampshire campaign manager for Gary Hart and President Jimmy Carter before she won the first of her three terms as governor, is exceptionally well connected with Democratic powers.

But Sununu, 44, whose father served three terms as governor before becoming George H.W. Bush’s White House chief of staff, began building his own networks as a three-term member of the House and, in the Senate, has traveled the world with John McCain.

This is a year that has proved to be a severe test for both McCain – the winner of the 2000 and 2008 New Hampshire presidential primaries – and for Sununu.

Demographic changes, particularly the migration of educated high-tech workers from Massachusetts and other states, and the popularity of Democratic Gov. John Lynch, have given the Democrats a new lease on life. In 2006, they took both House seats from the GOP and captured both houses of the Legislature. Though Barack Obama was upset by Hillary Clinton in last January’s primary, he never shut down his operations here – and has a formidable organization.

A poll in the Concord Monitor this week showed Obama with a seven-point margin over McCain and Shaheen with an identical lead over Sununu, though the Senate race tightens when only those firmly committed are counted.

Dante Scala, the head of the political science department at the University of New Hampshire and an expert on the state’s politics, commented that Sununu was “trying to climb a pretty steep mountain” even before the economic tailspin began last month. “He hoped to use her record on taxes as governor and her opposition to nuclear power and offshore drilling to bring her down.

“But the economy just knocked him into a ditch and he’s trying to figure out how to climb out.”

Sununu, like McCain, has struggled to convince voters that while he voted 90 percent of the time for Bush policies, he really is independent. He cites his opposition to an early Bush energy bill and his successful fight to add civil liberties protections to the Patriot Act.

He has a fan club on both sides of the aisle, and is talked about in Republican circles as a potential future presidential candidate.

The youngest member of the Senate has found himself running for re-election in one of the toughest years that Republicans have faced since 1974 – when Democrats elected their big class of “Watergate babies.”

His timetable is in serious jeopardy.