Bill Clinton has had his problems lately, but there's no doubt the former president is the best booster the Democratic Party has had since leaving office in January 2001. Even now, although he's clearly slowing down, Clinton is the party's most effective surrogate for wife Hillary.
Republicans haven't had the same luck. The only two-term GOP president in the last generation, George W. Bush, has stayed mostly out of politics in the seven years since he left the White House.
Bush's absence has caused some hard feeling among Republican politicos who wish they had a popular ex-president to bring more money and attention to GOP candidates. On the other hand, they know Bush's troubled time in office permanently diminished his post-presidential status. And now, to top it off, Bush, along with his father, former President George H.W. Bush, has taken the extraordinary step of refusing to endorse the presidential candidate of his own party.
In short, facing a difficult general election campaign and in need of all the help it can get, the GOP's ex-president situation is a mess.
George W. Bush left office with a job approval rating of just 28 percent after 9/11, two wars, and an economic collapse. He has since regained much of his popularity with Republicans. But even within his own party, Bush's status is shaky.
On Feb. 15, Bush broke his rule against campaigning to travel to South Carolina to appear at a rally on behalf of his brother Jeb. The Jeb Bush campaign was already in its final days, and there was nothing W. could do to save it. But W. still got a rousing reception.
Before the rally began, when the master of ceremonies asked the crowd, "Are y'all ready to see the president?" a huge roar went up. They weren't cheering for Jeb. The audience that W. attracted was by far the biggest of Jeb's campaign.
But at a Republican debate just a couple of days earlier, Donald Trump, who has criticized George W. Bush's presidency throughout the campaign, slammed the war in Iraq as "a big, fat mistake." Then Trump went further to say that George W. Bush "lied" the nation into war.
"They said there were weapons of mass destruction, there were none," Trump said. "And they knew there were none."
Jeb Bush stood haplessly by, unable to defend either himself or his brother.
It was a concise lesson in the ambiguities of George W. Bush's legacy for Republicans.
On the other hand, Bush could have helped his party by appearing at fundraisers and other events where an ex-president -- even an ex-president with a troubling legacy -- would still be a big draw. His refusal to do so has left some resentments.
Katon Dawson, a former chairman of the South Carolina Republican party, has no complaints about Bush's treatment of the state while in the White House. But afterward has been a different story.
"He was gracious to South Carolina -- eight visits, raised us money, wonderful access to the White House," said Dawson. "But then he went home and retired. We've asked him (to come), and the answer is no. The first time we saw him was when he came to bail his brother Jeb out."
Now Bush is likely to make relations with Republicans around the country even more difficult by refusing to support the GOP nominee. Some anti-Trump conservatives cheered the move, but state Republican parties are coming around to the reality of a Trump nomination.
But how could Bush support the candidate who slapped down his brother and trashed his own White House record? That would be a stretch even for a nimble politician.
Still, the refusal to support Trump makes Bush and his family look like they are putting personal interests over the party. And in the end, some Republicans wonder whether that might end up helping Trump.
"The ruling class, the establishment folks, the Nantucket-Kennebunkport-Lake Winnipesaukee crowd is opposed to Trump," said Curt Anderson, a top strategist for the Bobby Jindal campaign who is not part of any campaign now. "Trump is from a lower caste, he's too loud at dinner parties. I would be surprised to learn that their refusal to endorse is based on ideological concerns of any kind."
In the end, the Bush factor is too complicated to compute. A former president who is unpopular with many voters but popular with donors; who is pulled in different directions by family and party loyalty; who shies away from politics while his Democratic counterpart still draws crowds and moves voters.
Some Republicans like to send around a photo of a smiling Bush with the caption "Miss me yet?" The problem is, there's no clear answer.