As they played baseball Wednesday morning, Representative Steve Scalise, a congressional staffer and members of the Capitol Police were shot by an attacker.

The aggressor was then shot by Scalise's Capitol Police security detail and Alexandria police officers. Still, while no one appears to have died today, these events speak to an unyielding truth.

Protecting politicians is difficult.

The first complication is varied interests.

In the cultivation of support and votes, the politician's impulse is to maximize his or her availability to the public. Conversely, a protection officer's impulse is to keep the politician in a fortress.

That said, protecting politicians is more complicated than protecting other government officials such as senior Army officers (protected by the U.S. Army-CID) or federal judges (protected by the U.S. Marshals service). Unlike other officials, politicians are regularly approached by the public. This allows assassins to hide in plain sight instead of forcing them to keep their distance.

In 2005, for example, George W. Bush had a grenade thrown at him as he gave an open air speech in Tbilisi, Georgia. While the grenade did not explode, no one was aware of the assassination attempt until after Bush had finished speaking. Again, the assassin had used the chaos of the bustling crowd to get close to his target.

This threat motivates protection teams to maintain sanitized areas -- accessible only to relevant passholders and screened individuals -- around a protectee. Those individuals are not allowed to leave and re-enter the sanitized area until the protectee has departs.

Another difficulty is posed by finite resources. The protection afforded Members of Congress, for example, is more limited than that afforded to the President.

While the Capitol Police assigns protection details to certain high-ranking individuals, its counter-sniper, counter-assault, and explosive detection support teams are traditionally kept on Capitol Hill. Correspondingly, once off the Hill, a security detail is effectively on its own. Additionally, it would be impractical and unfortunate (in deterring public contact) to provide 24-hour security details to each of the 535 Representatives and Senators. Assuming eight officers (two per shift on a four shift rotation) per protectee, the Capitol police would need thousands more officers. Indeed, it would likely have to double in size.

As I say, that's unlikely to happen.

And so, it will continue to be up to exemplary officers to rise to the challenge.