Like most Americans, I wish we had more political leaders who made decisions beyond the narrow boundaries of their tribe, party or what James Madison called "faction." Americans may even be surprised to learn that the Constitution never mentions political parties and was largely designed to prevent partisanship from overwhelming the union. Sadly, our politics have evolved to give partisans more power.

Conventional wisdom holds that the presidency of George Bush left scars that distort his party still. This wisdom is gilded by a shockingly partisan new book, "It's Even Worse Than It Looks," by Thomas Mann and Norman Ornstein. Armed with anecdotes but not much more, they blame Republicans for the gridlock.

For example, the authors claim that ideological polarization lessened "after Democrats regained control of Congress in the 2006 midterm elections." Where's the evidence?

Recall that then-House Speaker Nancy Pelosi and Senate Democrats refused to even discuss Social Security with President Bush. No matter -- the blame-Republican crowd pays no heed to the do-nothing Dems of 2005 to 2008. Bush was a divider, they say. Just look at the divisive legislation his administration advanced!

Forgive me for being an economist and not a pundit, but I think we actually should look at the signature laws passed during Bush's presidency compared with Obama's -- the roll call votes in particular. For example, both presidents pursued major domestic policy reform immediately after inauguration -- education for Bush, health care for Obama. The results? No Child Left Behind passed both chambers in 2001 with 46 Senate votes from Democrats in the Senate and 197 votes from Democrats in the House. In contrast, Obama's health care reform was strictly partisan from day one. The White House ignored bipartisan overtures from Senate centrists, and the bill ultimately passed with no Republican votes in either chamber.

The adjoining chart expands the comparison to five signature laws from each president. This includes the Bush tax cuts of 2001 (formally known as EGTRRA), the Iraq Resolution, the PATRIOT Act, No Child Left Behind, and the Medicare Modernization Act of 2003. Compare the votes with recent legislation -- Lilly Ledbetter, the stimulus, Obamacare, Dodd-Frank and the repeal of Don't Ask, Don't Tell -- and you see a disturbing pattern of polarization by Obama and Democratic legislators.

The total number of opposition votes Obama attracted for all five signature laws was just 14 in the Senate and 21 in the House. The comparable numbers for Bush are 145 votes in the Senate and 468 in the House. The number of House Democrats who voted for Bush's Iraq War authority is four times the number of House Republicans who voted for all five Obama bills combined.

Skeptics may interpret all this is a sign of Republican intransigence since 2009, but that is self-deception. When has Obama ever genuinely proposed centrist legislation? He kicked the can of budget responsibility down the road with his Simpson-Bowles commission, then ignored the commission's final report. The Obama White House never sought centrist policy or votes in its signature legislation, not even from centrist Democrats. Consider the 34 Republican representatives who voted against Bush's NCLB because they thought it too liberal, in contrast with the 33 House Democrats who voted against Obama's Patient Protection and Affordable Care Act because they found it too liberal.

Mann and Ornstein can point fingers to the Right, but the math points the other way.

Tim Kane is the chief economist at the Hudson Institute in Washington.