More than a dozen Senate Republicans encouraged government watchdog groups Wednesday to investigate Senate Democrats for mixing politics with policy in consideration of a terrorism reinsurance bill at the Senate Banking Committee last month.

In a letter to leading watchdog groups, Senate Republican Conference Chairman Rick Santorum (Pa.) and 16 other Senate Republicans said the groups should look into allegations that Democrats on the panel decided to drag their feet on the reinsurance measure — a top industry priority — after insurance lobbyists scheduled a fundraiser for the Republican who is challenging Minority Leader Tom Daschle (D-S.D.) this fall.

“As non-partisan watchdogs of Congress, we are confident that your organizations are dismayed at such an explicit link between legislative activity and political contributions,” the GOP Senators said in a letter to Common Cause, the Center for Responsive Politics, Democracy 21, Public Citizen and Citizens for Responsibility and Ethics.

Senate Republicans asked the groups to look into the matter as the Republicans consider taking their own steps.

The Senators also called on the groups to pursue the investigation with the same intensity that they have pursued ethics complaints against Republican lawmakers such as House Majority Leader Tom DeLay (R-Texas).

“It is our hope that you intend to aggressively respond to this situation, just as you have so faithfully pursued actions against Members of Congress for more obtuse breeches of the relationship between politics and public officials,” the letter said.

The letter was organized by Santorum and signed by Sens. Mitch McConnell (Ky.), George Allen (Va.), Trent Lott (Miss.), Ted Stevens (Alaska), Pete Domenici (N.M.), Chuck Grassley (Iowa), James Inhofe (Okla.), Craig Thomas (Wyo.), Norm Coleman (Minn.), Wayne Allard (Colo.), Larry Craig (Idaho), John Cornyn (Texas), Mike Enzi (Wyo.), John Ensign (Nev.), Jon Kyl (Ariz.) and Jeff Sessions (Ala.).

The GOP letter comes roughly a week after Roll Call reported that Senate Democrats had decided to drag their feet on the terrorism reinsurance bill after insurance industry lobbyists planned to raise money for Rep. John Thune (R-S.D.), who is seeking to oust the Democrats’ minority leader.

Lobbyists for the insurance industry began circulating invitations to the June event just a few days before the Senate Banking, Housing and Urban Affairs Committee held a hearing on the terrorism reinsurance bill.

The $1,000-a-plate dinner, scheduled for June 10 at the Occidental Grille, was sponsored by the American Insurance Association and the Property Casualty Insurance Association of America along with a half-dozen insurance companies.

“We all know the importance of this Senate race, so please consider joining us,” wrote Eric Rizzo, a lobbyist for Farmers Insurance Group, in a fundraising pitch that accompanied the invitation.

After Democrats found out about the industry’s efforts to defeat Daschle, they decided to stop their once-active efforts to enact the industry’s terrorism reinsurance bill.

One Democratic aide, speaking on the condition of anonymity, said last week that “there was a palpable difference in terms of the tone and willingness” of the party to push the terrorism reinsurance bill after word of the GOP fundraiser leaked out. “At this point, that hearing is the end of the road.”

Though Democrats said they would still vote for the bill, the move amounted to killing the legislation because the industry had been depending on Democratic lawmakers to push the bill. Republicans and the Bush administration had shown little enthusiasm for renewing the terrorism reinsurance backstop when it expires next year.

The dinner was originally scheduled for June 10, but it was subsequently postponed. Insurance industry lobbyists now hope to hold the dinner during the week of July 19.

The insurance industry event, which aims to net $25,000 for Thune, is part of a series of events planned by Washington lobbyists to raise $500,000 to defeat Daschle in November.

The events, collectively known as “Team Thune,” were started earlier this year when it became clear that Daschle was raising far more money from corporations and Washington lobbyists than Thune.