Why the leftist love for TR? Parker ran to his left.
Um.........
Having lost the 1904 election badly with a conservative candidate, the Democratic Party turned to two-time nominee William Jennings Bryan, who had been defeated in 1896 and 1900 by Republican William McKinley. Despite his two previous defeats, Bryan remained extremely popular among the more liberal and populist elements of the Democratic Party. Despite running a vigorous campaign against the nation's business elite, Bryan suffered the worst loss of his three presidential campaigns.
http://en.wikipedia.org/wiki/United_States_presidential_election,_1908
Yes, which is like a historian pointing out that the Democrats nominated a conservative candidate in 1992. It doesn't necessarily mean he ran to Roosevelt's right just like Bill Clinton didn't run to the right of George HW Bush.
While I won't make the case that Alton Parker ran to Teddy's left, it's pretty hard to make the assumption that Teddy Roosevelt was running to his left. Roosevelt, after all, praised and expanded the militarist tendencies embraced by his predecessor McKinley (ie, expand the American Navy so we can spread our market of influence abroad) and supported the general conservative Republican platform of the time of low taxes, high tariffs, and support of the Gold Standard. Sure you could say he made some conciliatory statements towards labor, but so did McKinley.
By that time, a more neutral response to labor was required. And while I will not argue that Teddy Roosevelt's stance was that of a hardline conservative, it was hardly as pro-labor as LaFollette Republicanism or *gasp* Tammany Hall!
Now I am not going to do the same bit about how Ted didn't really advance any serious left wing agenda, but I will just say that Alton Parker's campaign basically looked at Teddy's 1st term and was like "yeah, I think Ted is a real cool guy, he's anti-monopolist and doesn't afraid of nothin! Okay I guess Imperialism is a little excessive and I wish he was more pro-free trade!" The idea that he was running as a pro-monopolist who strongly protested Roosevelt's first term is hilarious and can be easily debunked just by reading the wikipedia entry on the 1904 Election Campaign.
And yes, just like Roosevelt he accepted money from Big Business hand over fist while making some small noise about the need for "reform".
What made the 1904 Election remarkable was how much the two men agreed on the basic issues and how much of a "good spirited" campaign it was compared to the previous two elections when the American people had two pretty distinct choices to choose from.
To make a more recent parallel here, Teddy Roosevelt is Dubya and Parker is Gore.