Gold prices are back on a rallying mode thanks to subdued greenback and political uncertainty. The largest gold ETF SPDR Gold Shares GLD has gained about 10.2% in the year-to-date frame (as of July 31, 2017) and was up about 4% in the last one month. Last month’s gain followed gold’s first monthly drop of this year in June (read: Top ETF Stories of July 2017).It seems that gold is up for more gains in the near term. The DoubleLine Capital CEO Jeff Gundlach sees the precious metal "coiling”. Below we highlight a few factors that could trigger a gold rally ahead (read: What Do Mixed Earnings Mean for Gold Mining ETFs?).Safe Haven Demand The wind beneath the wings could be a rise in safe-haven demand in the wake of heightened volatility in the global market. The political debacle was rife in the month with the failure of Trump’s healthcare bill.The collapse of the bill in the Senate triggered concerns over the passage of Trump’s other pro-growth policies like tax cuts, deregulation and infrastructure spending. Plus, North Korea’s occasional missile launches pushed up the value of gold.Dollar’s Weakness Political upheaval in Washington, some weak U.S. economic data and a still-dovish Fed capped the dollar’s strength. Subdued inflation is actually holding the Fed back from being too aggressive on the policy-tightening issue. Powershares DB US Dollar Index Bullish Fund UUP lost about 3.3% in the month. Since these commodities share an inverse relationship with the greenback, the yellow metal can gain ahead (read: Why You Should Bet on Blue Chip ETFs Now).Relatively Cheaper ValuationGundlach believes that gold prices would gain because "gold looks cheap compared to markets that have rallied a lot.” The Relative Strength Index for GLD is presently 66.37, suggesting that the fund is yet to enter into the overbought territory.Any Threat Ahead?Gold buying in India – a key consumer of gold – declined asthe country launched GST (goods and services tax) on July 1 in order to fill in for/unite more than a dozen of indirect taxes levied by state and central governments. Under the GST norm, taxes on gold increased to 3% from 1.2% previously. Meanwhile, a rising gold prices also hurt the retail demand for gold (read: India to Unify Tax: Near-Term Pain/Long-Term Gain for ETFs).However, to beat GST, Indian consumers looked to Dubai for buying gold and jewelry. Retailers in Dubai witnessed higher demand among Indian travelers. The trend can provide some boost to gold buying till Dubai enacts its own sales tax later this year.Bottom LineAs of now, the metal seems due for a rally, though the run may not be for long enough. So, investors intending to profit out of the new-found optimism in the gold space may consider gold ETFs like GLD, iShares Gold Trust IAU and ETFS Physical Swiss Gold SGOL.For fatter returns, investors can also play leveraged products like VelocityShares 3x Long Gold ETN UGLD, DB Gold Double Long ETN DGP and ProShares Ultra Gold UGL. However, leveraged ETF plays involve greater risk.Want key ETF info delivered straight to your inbox? Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report ETFS-GOLD TRUST (SGOL): ETF Research Reports GOLD (LONDON P (GLD): ETF Research Reports ISHARS-GOLD TR (IAU): ETF Research Reports PRO-ULT GOLD (UGL): ETF Research Reports PWRSH-DB US$ BU (UUP): ETF Research Reports VEL-3X LNG GOLD (UGLD): ETF Research Reports DB GD 2XL (DGP): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report