AUGUSTA — Sen. Olympia Snowe, who has never lost an election or had to win a primary, is suddenly defending her job against a host of challengers from all angles.

At least ceremonially, it grew by one Saturday when Matt Dunlap, a former Maine secretary of state, announced his candidacy in his hometown of Old Town. It’s been known for weeks that Dunlap planned to run against state Rep. Jon Hinck of Portland for the Democratic nomination.

On the Republican side, Snowe faces a primary challenge for the first time, and from two candidates. They are Scott D’Amboise of Lisbon Falls, who lost a Maine congressional election in 2006, and Andrew Ian Dodge of Harpswell, a freelance writer who has acted as a spokesman for the tea party in Maine.

The field spans a diverse range of the political spectrum, from a former environmental lawyer and self-described progressive in Hinck to tea partiers D’Amboise and Dodge.

The two GOP challengers have been sniping for weeks at Snowe, who has held the Senate seat since 1994 and is seeking her fourth term. D’Amboise has challenged her on issues from judicial appointments to the health care overhaul and gays in the military, while Dodge labeled her as a foot soldier among the “tax and spend partisans.”

The two tea partiers have also shown more of a tendency to engage each other than the two Democratic primary contestants.

So far, Snowe has trained her verbal guns mostly on Congress.

“She is frustrated with the partisan gamesmanship in Washington and shares the anger Mainers feel about Congress’ inability to get things done,” her campaign says.

While Hinck came north to Dunlap’s backyard in Orono to announce his candidacy, Dunlap chose to announce in his hometown. While the two may have different views on some issues, they have agreed to lay off each other before the primary, said Dunlap.

“We’re both keeping our eyes on the prize,” he said.

Hinck put out a statement last week commending Dunlap for entering the race and setting his sights on the Senate seat.

So far, Snowe is far ahead of any challenger in campaign funding, with $3.2 million in cash on hand as of Sept. 30, compared to D’Amboise’s $182,000, according to Federal Election Commission filings. The FEC said Dodge, Dunlap and Hinck had not reported financial activity to that date.

Her track record for winning and her financial edge will not distract Snowe, her campaign says.

“Senator Snowe’s approach to this race will be the same as her approach to everything she does,” said a statement from her campaign. “She is working hard, taking nothing for granted, listening carefully to her constituents, serving as a fierce advocate for Maine’s interests and battling to find thoughtful solutions.”