WASHINGTON - Although they face little challenge from opponents, Massachusetts Democrats are not taking chances in funding their congressional re-election bids, according to campaign finance reports.

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Four-term Democrat Rep. Martin Meehan of Lowell had approximately $1.6 million on hand on Monday, the end of the filing period for last year. That's despite having no announced challenger.

Much of Meehan's sum, the most of any Massachusetts candidate whose reports were available Monday, was carried over from the last campaign when he also ran unopposed and ended up with more than $1 million left over.

The reports had to be postmarked by Monday but were not necessarily available for viewing. Reports for Democratic Reps. John Tierney of Salem and Michael Capuano of Somerville were not available and were not distributed by their offices.

Meehan also raised and spent the most of any candidate this period. He took in approximately $369,000 and used about $123,000 on campaign-related activities.

While he hasn't heard about an opponent yet, Meehan said he's not about to take any chances. "The Republicans are targeting me. They keep saying they are going to get someone to run."

Among those with smaller warchests is incumbent Democratic Rep. John Olver of Amherst, who recently learned he has gained a viable opponent.

Olver, who is in his fourth term, raised $129,783 in the period. He spent $43,636 and wound up with more than $270,000 cash available.

Peter Abair announced last week he would quit his state job today to run against Olver. Abair was director of municipal development for the state Office of Communities and Development and formerly headed Republican Gov. Paul Cellucci's western Massachusetts office.

Olver will not comment on the race until Abair becomes an official candidate, according to a spokeswoman.

Abair admits his late entry may add a hurdle to the race but he says it's one he can overcome.

Olver's fund-raising reports, especially compared to those of others in his party, suggest he "is not as strong a candidate for someone who's a four-term incumbent as he might be," Abair said.

Twelve-term Democratic Rep. Edward Markey of Malden, who is unopposed, raised $125,966 and had a little over $1 million on hand. Approximately $750,000 was left over from the last election.

Rep. William Delahunt, a Quincy Democrat, raised $328,964 this period for his race against mental health counselor Thomas Tavener. Delahunt's available cash total is $824,744.

Tavener, who has never run for political office, does not have to file a report with the Federal Election Commission because his campaign has raised less than $5,000.

The candidate with the least money is one of the state's longest-serving members, Newton Democratic Rep. Barney Frank. Now in his 10th term, Frank raised only $15,352 this reporting period and spent more than $68,000, leaving him with $136,338 on hand.