TO GOVERN IS TO SUPPORT TRADE:

The importance of exports to metro economies has opened a revealing divide between House and Senate Democrats, who are mostly resisting Obama's request for expedited Trade Promotion Authority, and Democratic mayors, who are mostly supporting it. The U.S. Conference of Mayors, which is dominated by Democrats, has endorsed the Trans-Pacific Partnership deal and the trade-promotion authority for Obama. Providing Obama with expedited legislative authority and completing the Asian deal, which would lower trade barriers among 12 countries including America, "is a critical step to ensuring that the United States and its metro economies remain leaders in the global market place," conference president Kevin Johnson of Sacramento and vice-president Stephanie Rawlings-Blake of Baltimore, each African-American Democrats, wrote to Senate leaders on May 12.

Houston Mayor Annise Parker, also a Democrat, was even more emphatic in a conference call with reporters. "We live on trade," Parker said of her city. "It is important to our economy, it keeps people employed, and we absolutely believe it's our future."

New data released May 13 by the Brookings Institution's Metropolitan Policy Program helps explain the mayors' tilt toward trade. Though overall U.S. exports first slowed, and then declined after early 2014, Brookings found that fully 86 percent of U.S. exports now originate from urban areas. Moreover, exports drove more than one-quarter of all metro area economic growth from 2009-2014. "This has metro leaders and elected officials placing an increasing focus on exports as a way to grow and maintain their regional economies," said Bruce Katz, the Metropolitan Policy Program's codirector, in an email. In their letter to Senate leaders, Johnson and Rawlings-Blake indicated the conference's own forecast projects that exports will account for one-third of metro areas' economic growth in coming years.

The cities at the very top of the list for export-related jobs overwhelmingly tilt toward the Democrats. The Metropolitan Policy Program's analysis found that the cities that generate the most jobs from exports include such Democratic bastions as New York, Los Angeles, Chicago, Houston, Seattle, Dallas, Boston, San Francisco, Washington, D.C., Detroit, Philadelphia, Atlanta, Portland, San Jose, and Minneapolis.

In all of those cities, Brookings calculates that exports support at least 132,000 jobs. Export-related jobs account for around one-in-six of all jobs in the Seattle metro area, about one-in-seven in Portland, Oregon, and San Jose, California, about one-in-eight in Houston and San Francisco, and roughly one-in-nine in Los Angeles, Miami, and Detroit, the analysis found. Exports contribute just over one-in-ten jobs in New York, Boston, Charlotte, and Las Vegas, and just slightly less than one-in-ten in Chicago, Dallas, and San Diego. (The Metropolitan Policy Program calculates metro-area jobs linked to exports by adding the direct jobs supported by export revenue, the jobs created by businesses supplying parts or services to the exporting industries, and jobs in freight and transportation related to shipping goods abroad.)

Democrats now control the mayor's office in 18 of the 20 cities that anchor the metro areas that Brookings found derive the most jobs from exports. (The only exceptions are Republicans Kevin Faulconer in San Diego and Tomas Regalado in Miami.) More relevant to Obama's immediate challenge, a Next America analysis found, Democrats control 121 of the 203 House seats mostly situated in those 20 metropolitan areas. That means Democrats now control about three-fifths of all the House seats in the metro areas producing the most jobs from exports. Put another way, representatives from just these 20 high-export metro areas account for almost two-thirds of all 188 House Democrats.

Follow @brothersjudd