After making a hideous, filibustered mess of campaign finance reform this fall, the Senate now will hold a straight up-or-down vote by March. Citizens who desire cleaner elections should thank their local pothole.

After doing his level best — or worst — to block changing a system awash in money and misleading ads, Senate Majority Leader Trent Lott on Thursday abruptly changed directions and agreed to put the McCain-Feingold bill back on the table. Quite a turnaround for a senator who on Monday said the reform package was dead for this year and for as many years to come as he could arrange.

Why the reversal? Democrats, clambering for the high ground throughout Senate hearings on campaign abuses, vowed to stall every bill in the hopper except the most urgent until McCain-Feingold got a simple majority vote. Among the potential hostages was the highway bill, a six-year measure to return some $145 billion to the states for transportation projects.

Thousands of road, bridge, airport, rail and marine projects were threatened, thousands upon thousands of construction jobs were in jeopardy. The outpouring of outrage was swift and violent as senators learned the hard way what they should have known all along — don’t play games with the highway money. Suddenly, McCain-Feingold was breathing again and the highway bill was set free.

The irony here is that the opportunity to clean up a situation most Americans detest — the undue influence of big money on politics — comes as a result of employing a tactic most Americans loathe — the attachment of unrelated amendments to crucial legislation. Republicans tried it last spring with disaster relief and got pilloried as being more concerned about how Census 2000 was to be run than they were about flooded Dakotans. Democrats threatened to do it with the highway bill and pulled it off. It rarely happens, but two wrongs occasionally can give right a fighting chance.

Of course, McCain-Feingold is not out of the woods. The only guarantee is that a simple majority vote on Lott’s proposal to table the measure will be held by March 6. If McCain-Feingold survives that test, it will be fair game for the same tinkering, posturing and unacceptable amending that blocked it last month.

Maine Sens. Olympia Snowe and Susan Collins are on record saying they will oppose Lott’s attempt to table McCain-Feingold, but that’s just a start. Deep divisions remain between the two parties, particularly in regard to contributions from labor unions, membership organizations and corporations. Five months is ample time to resolve those differences — Snowe’s call for a bipartisan working group to do just that is a good idea — but a lot of arm-twisting and deal-cutting can occur between now and March as well. Campaign finance reform could be headed down another dead end, but at least it will be freshly paved.