Remember "compassionate conservatism"?

That was the message that then Texas Gov. George W. Bush ran on when he sought the presidency in 2000, a mantra that was aimed at re-inventing the Republican party by casting it as caring and committed to core values, more interested in uniting than dividing. "We will prove that someone who is conservative and compassionate can win without sacrificing principle," Bush said on the day he announced his presidential campaign in Iowa in the summer of 1999.

It's ironic then that what Bush's presidency ushered in was a period of hyper-partisanship, the likes of which we hadn't seen in modern political history -- and through which we continue to slog.

The first shows that of the 10 most polarized years in terms of how the two parties view the president, nine have come in the years since George W. Bush took office.  (The polarization number is determined by the difference between a president's approval rating with Democrats and his approval rating with Republicans.) Bush accounts for the 2nd, 3rd, 4th, 7th and 10th most polarizing years. President Obama accounts for the 1st, 5th, 6th and 8th most polarizing years. (Bill Clinton's 1996 is the only pre-2001 year to crack the top 10.)

The second chart details the average party gap in terms of approval ratings for every president since Dwight Eisenhower. The two biggest average gaps? You guessed it: Bush (#2) and Obama (#1).

It's clear that Bush's ascendancy to the presidency began a period of previously unmatched partisanship in our politics. (There is a case to be made that the extreme polarization began during the Clinton presidency -- particularly during the impeachment proceedings -- but Clinton's ability to win over Republicans by the end of his term contradicts that idea somewhat.)

What's less clear is the why -- and how much responsibility Bush personally bears for this polarization.

From the start, Bush's presidency divided the country.  He was one of four presidents to lose the popular vote while being elected thanks to winning the electoral vote. It was 32 days between the 2000 election and the Supreme Court decision that ended the legal fight and effectively gave Bush the presidency.

Bush's resistance to governing from the middle after such a divided result enraged those who had voted against him and who believed (and believe) that he was not the legitimately elected president. "With the advantage of extensive pre-transition planning his administration hit the ground running," reads a history of the Bush presidency at the Miller Center at the University of Virginia. "In his first six months in office, Bush had accomplished most of his 2000 campaign trail agenda."

Then came Sept. 11, 2001, a day that changed his presidency and the country in ways with which we continue to grapple today.  What Bush did in reaction to those terrorist attacks -- most notably his decision to invade Iraq based on an ultimately incorrect conclusion that Saddam Hussein possessed weapons of mass destruction -- set the course for all the partisanship that followed.

While Bush's job approval rating has bumped up to 47 percent in the most recent Washington Post-ABC poll, almost six in ten respondents still disapprove of his decision to invade Iraq. Almost three-quarters of Democrats (73 percent) still disapprove of that decision as do 60 percent of Independents; nearly four in ten Republicans disapprove of Bush's going into Iraq.

Of course, Bush didn't operate in a vacuum. The growth of talk radio, 24-hour cable news and the increased silo-ing of the media -- conservatives read/listen to conservative talkers, liberals read/listen to liberal talkers -- played a major role in pushing people deeper and deeper into their partisan camps. In a world in which people didn't live near (or even know)  anyone they respected who disagreed with their political views, partisanship ran wild. (Sometime in the 2000s the idea of "reasonable people can disagree" died.)

But, circumstances aside, Bush was quite clearly a catalyst in the increasingly partisan mixture of American politics. And, while policies like Iraq or his 2001 tax cuts or how he handled the aftermath of Hurricane Katrina all played a role, it's the way in which he went about the job that may well be most responsible for the divisiveness with which he is viewed and which defined not only his presidency but our current political climate.

Bush was not a second-guesser. He didn't apologize or back down from the direction he led the country -- then or now. Michael Gerson, a longtime Bush speechwriter and now a columnist for the Washington Post, wrote of his former boss: "Bush’s frankly moral approach, on other issues, is precisely what enraged his critics. But more than most, he is a leader of undivided sentiments."

Undivided sentiment to his allies.  Rank partisanship to his enemies. Regardless of where you come down on that question, it's clear that George W. Bush's presidency -- whether the man, the times or, most likely, a combination of the two  -- brought the country into a period of historic levels of partisan polarization.

It's where we still are.