Sen. Michael B. Enzi’s sluggish fundraising over the first six months of the year wasn’t a problem until Tuesday, when Liz Cheney announced she would challenge the Wyoming Republican in a primary.

Suddenly the third-term incumbent, who has spent a total of $4.2 million in three drama-free elections to the Senate, is among a cadre of vulnerable incumbents preparing for costly contests in 2014.

Besides Enzi, who tied with another senator on retirement watch for the lowest second-quarter haul among incumbents, the rest of the targeted senators in the class are fundraising aggressively. In fact, most are keeping up with and, in some respects, surpassing the torrential fundraising pace of the 2012 cycle.

(See also: Roll Call’s 2014 Senate FEC Fundraising Chart)

Sens. Mark Begich, Kay Hagan, Mary L. Landrieu and Mark Pryor — the Democrats running in the toughest terrain — are all building up significant war chests capable of competing against the forthcoming media assault from challengers and outside groups. Like Enzi, they’re all running in states with relatively inexpensive media markets.

Begich raised almost $1 million for the second straight quarter; Hagan is approaching $4 million raised this year; Landrieu is staying a step ahead of the hard-charging Rep. Bill Cassidy, R-La.; and Pryor has a nearly 4-to-1 cash advantage over potential challenger Rep. Tom Cotton, R-Ark.

On the other side of the aisle, Senate Minority Leader Mitch McConnell in Kentucky is taking no chances in his fifth re-election campaign. After leading all other senators in second-quarter fundraising, McConnell was sitting on almost $10 million in the bank as of the end of June.

He’s finally got a challenger in Kentucky Secretary of State Alison Lundergan Grimes, who will formally kick off her campaign July 30 and file her first fundraising report about two months later.

Of course, raising money is no silver bullet for sitting senators of either party. The only two incumbents to lose last cycle, Republicans Scott P. Brown of Massachusetts and Richard G. Lugar of Indiana, were out to monumental head starts at this point in 2011.

Nearly identical to McConnell, Brown had $9.6 million in the bank as of June 30, 2011, and no opponent to speak of — though he was running in a far different state politically. Now-Sen. Elizabeth Warren, D-Mass., didn’t enter the race until September.

Lugar had $3.5 million on hand at this point in 2011, while state Treasurer Richard Mourdock had a measly $203,000. Mourdock went on to defeat Lugar less than a year later with help from deep-pocketed, conservative outside groups.

Likewise, Arkansas Democrat Blanche Lincoln’s fundraising through the second quarter of 2009 closely mirrors Pryor’s this cycle. She ended up being forced to spend some $9 million in the primary before getting trounced in the general election.

With less than half a million dollars in the bank, Enzi hardly has an edge at all over Cheney, the elder daughter of former Vice President Dick Cheney, who is a former Fox News contributor and State Department official. She’s likely to be able to raise significant funds nationally.

Enzi conceded to reporters on Tuesday that fundraising has “always been a problem” for him, but on Wednesday he downplayed the importance of cash in the Cowboy State.

“It doesn’t take them long to make up their mind,” Enzi said of Wyoming voters in an interview with CNN. “And it doesn’t cost a lot of money to have them make up their minds.”