The health-care sector is often considered a tried-and-true investment with solid long-term upside potential as an aging population requires increasing amounts of medical care.

But this consistent earner is looking a bit sickly compared to the broader market as the S&P health-care select sector index is up 2 percent year to date versus the S&P 500, which is up 11 percent. Given the healt-care sector’s usual haleness, does the current underperformance represent a chance to buy the dip, or is it a sign the lethargy is masking other infirmities?

Katherine Schoen, manager of private wealth management equity and fixed-income research for Baird, says health care might be under the weather for a while because of politics. Whether its Democratic candidates discussing changes to the current health-care system with a “Medicare for all” program, or bipartisan interest in Congress to improve drug-pricing transparency, health care is in the political crosshairs on several fronts, she says.

“That’s what the headwind is,” Schoen says. “That why these multiples haven’t kept up with their defensive peers and why performance hasn’t kept up. What the market doesn’t like is the unknowns.”

Nick Kalivas, senior strategist at Invesco, concurs with Schoen. From a broad perspective, health care typically has the demographic trend of an aging population and the growth potential of product innovation going for it. Plus, it often finds favor with investors at this point in the economic cycle. However, this time is different because of politics.

“I think it’s probably going to be a headwind here for the foreseeable future,” he says.

Nothing is likely to get done in Congress until after the election and people will want to see what is the leadership in Washington in 2020, Kalivas says. That could mean the health-care sector is going to be sensitive to polling data and expectations for how the election plays out.

Given the sector’s weakness, it’s not surprising some the top broad-based health-care exchanged-traded funds are looking a bit wheezy in performance terms.

The Health Care Select Sector SDPR Fund (XLV), the oldest of the health-care ETFs and the largest at $17 billion in assets under management, is up 2 percent year to date. It’s a market cap-weighted fund that follows the S&P Health Care Select Sector Index. The top sector is pharmaceuticals at 43 percent, with health-care equipment at 27 percent and health-care providers at 13 percent. Johnson & Johnson is the fund’s biggest holding at 11 percent, with UnitedHealth Group and Pfizer each at 7 percent. Its expense ratio is 0.13 percent.

The fund has returned 7 percent during the past year, and is up 9 percent on a three-year annualized basis and 9.7 percent on five-year basis. Comparatively, the SPDR S&P 500 Trust (SPY) is up 12 percent year to date and 4.3 percent during the past year. Its average annual three-year return is 12 percent and its average five-year return is 10 percent.

Another market cap-weighted health-care behemoth ETF, the Vanguard Health Care ETF (VHT), has a slightly better year-to-date performance versus XLV with a return of 3.7 percent. It has a one-year annualized return of 6.5 percent, a three-year average return of 10 percent and a five-year return of 10.5 percent. It has $9 billion in AUM and an expense ratio of 0.10 percent. It follows the MSCI U.S. Investable Market Health Care 25/50 Index.

It has a slightly different sector mix than XLV, although its top three individual stock names are the same. Pharmaceuticals is its top sector at 38 percent, health-care equipment is 27 percent and biotechnology is 14 percent. Johnson & Johnson is the fund’s biggest holding at 9 percent, with Pfizer at 6 percent and UnitedHealth Group at 5.6 percent.

The Invesco DWA Healthcare Momentum ETF (PTH) is a smart-beta ETF that's faring a little better performance-wise than the two market cap-weighted funds. It has gained 11.6 percent this year, but is down 8 percent on a one-year annualized basis. It’s up 20 percent on a three-year annualized basis and 11 percent on a five-year basis. It has $139 million in AUM and an expense ratio of 0.60 basis-points.

PTH’s top sector is health-care equipment at 40 percent, with biotechnology at 30 percent and health-care providers at 18 percent. Exact Sciences is its top stock at 6.2 percent, with Mirati Therapeutics at 6 percent and Axsome Therapeutics at 4.7 percent

Kalivas says PTH’s strategy is to chose stocks based on relative strength or momentum, and it can move across the market-cap sector. As it rebalances, PTH tries to buy the winners or emerging winners and remove those that are starting to struggle. He says 80 percent of the outperformance is attributed to the stock selection.

Investors who might consider buying into the broader health-care sector on the current weakness need to think about how the current political climate is shaping up and not base their decision on the usual valuation metrics, Schoen says.

“You can say something fundamentally looks undervalued, but it’s going to have a valuation discount to the market because there are uncertainties around the group,” she says.