When a U.S. president gets deep into a second term, there are certain things that you can count on.
Political victories are tougher to come by.
The battle scars are deeper.
Public approval falls, and the opposing party looks for new ways to gain some advantage.
And in the modern presidency, there's another second-term development that's becoming just as predictable as the list above — calls for the president to be impeached.
It happens even when there's little — or no — chance of success.
Let's start after Richard Nixon, who resigned during his second term, before his certain impeachment and conviction in the U.S. Senate could play out.
Of the two-term presidents who followed, Democrats talked of impeaching Ronald Reagan during the Iran-Contra scandal; Bill Clinton was impeached by the GOP-controlled U.S. House following revelations of his relationship with White House intern Monica Lewinsky; liberal Democrats brought articles of impeachment during George W. Bush's eighth year in office, citing the decision to go to war in Iraq, torture of detainees and other issues; and now, after nearly six years in office, there are growing calls for President Obama's impeachment by Tea Party Republicans and others, including Rush Limbaugh and Sarah Palin.
"The one tool they [the Congress] have are the articles of impreachment," the former Alaska governor told Fox News. "Let's get going on that."
But most of the noise for impeaching Obama is coming from outside Congress. When House Speaker John Boehner was recently asked about Palin's statement he said, curtly: "I disagree."
Instead, Boehner says he will sue the White House. That move does not satisfy those who want to press for impeachment over a list of issues ranging from how the president has implemented the health care law to objections over recess appointments to his handling of immigration to the controversy over IRS scrutiny of Tea Party groups seeking tax-exempt status.
Surely Boehner has vivid memories of how the impeachment of Clinton played out in 1998 and 1999.
The GOP was seen as vindictive and overreaching — and the Clinton presidency survived.
Not only that, but Clinton saw his popularity rise, and Republicans suffered political troubles as a result.
Political scientist George Edwards of Texas A&M says today's impeachment advocates ignore the lessons of the Clinton years. He says it's all part of our deeply polarized politics.
"When one side sees the views of other side as not only wrong but illegitimate," Edwards says, "it provides grounds in their minds for an extreme measure such as impeaching the president."
And while impeachment talk might help fire up the Republican base in some places, there's also a chance it'll motivate the president's supporters who might otherwise not be as enthusiastic about voting in this election year, perhaps helping Democrats in some tight U.S. Senate races.
Further, professor Andra Gillespie of Emory University says, African-American voters are no doubt watching the talk of impeachment very closely. "There's been a lot of theorizing that blacks rally around the president in large part because of the perception that some of the opposition towards him is racially motivated," Gillespie says.
In fact, there are plenty of conservative Republicans warning about handing the Democrats an issue during the midterms. But that doesn't sway those pushing Obama's impeachment — even if they know it won't happen.
Call it rhetorical impeachment.
It's a tactic that's probably here to stay, but it's a far cry from the seriousness of the real thing.