In a surprising one-two punch, Democratic Sens. Byron Dorgan (ND) and Chris Dodd (CT) have let slip their plans to leave Congress at the end of this year.

Senate Banking Committee Chairman Chris Dodd (D-CT) is set to announce his retirement today. Photo: Daylife.com

Dodd’s retirement is much less troublesome for Democratic leaders than Dorgan’s — a strong replacement candidate already has emerged in Connecticut — but both departures could deal a blow to the prospects for passage of more transit-centric federal transportation bill this year.

As chairman of the Senate Banking Committee, which has jurisdiction over transit, Dodd showed strong support for clean transport funding. He has significant unfinished business on the table in his panel, in the form of legislation that would formally approve the Obama administration’s inter-agency sustainable communities effort and authorize $4 billion in transit-oriented development grants.

With Dodd’s record on Wall Street regulation seen as a major factor in his fall from grace, as well as crucial to burnishing his legacy, momentum for the transportation-and-housing bill could flag in 2010 as the retiring senator focuses on pushing financial reform across the finish line.

In addition, the Democrat next in line to lead the Banking panel is Sen. Tim Johnson (SD), who has taken a generally positive approach to transit but represents a highly rural state where sustainable development is less of a factor. (Another Democrat potentially in the hunt to succeed Dodd at Banking, provided that Democrats keep their majority next year, is the more transit-centric Sen. Jack Reed [RI].)

Dorgan’s unexpected retirement raises more subtle political questions. As one of two senators tapped by Majority Leader Harry Reid to coordinate the upper chamber’s coming job-creation bill, Dorgan remarked last month on the importance of beefing up merit-based infrastructure spending in that measure.

Nonetheless, the North Dakotan was counted as a definite opponent of cap-and-trade climate legislation that stands to send more than $1 billion in annual grants to clean transportation.

Perhaps the biggest negative consequence of Dorgan’s loss, then, is the fact that Republican Gov. John Hoeven is considered the frontrunner to take over his seat — with few if any strong Democrats in the mix to oppose him.